杨梅黄素及蛇葡萄素对酪氨酸酶的抑制作用

杨梅黄素及蛇葡萄素对酪氨酸有显著的抑制作用,２ｍｍｏｌ／Ｌ的Ｌ－多巴浓度下,５０％抑制的药物浓度分别为０．０８２ｍｍｏｌ／Ｌ及０．２０８ｍｍｏｌ／Ｌ,用Ｌ－多巴作底物,蛇葡萄素对酪氨酸酶是竞争性抑制,其Ｋ是０．０８５ｍｍｏｌ／Ｌ;而杨梅黄素对酪氨酸酶则是混合性抑制,其Ｋｉ与Ｋｆｉ分别是０．０２６ｍｍｏｌ／Ｌ与０．０７２ｍｍｏｌ／Ｌ。     

蛇葡萄素提取工艺研究

本文利用新方法从中药粤蛇葡萄中提取其主要化学成分蛇葡萄素,收率达１０％。     

羽叶蛇葡萄中的一个新酚甙

从羽叶蛇葡萄(Ampelopsis chaffanjonii(Levl)Rehd.)茎部乙醇提取物中分得的一化合物,经波谱分析确定其结构为一新酚甙,命名为蛇葡萄素。     

氨基葡萄糖对酪氨酸酶的抑制作用

通过对酪氨酸酶催化底物L-DOPA反应速率的观察测定,研究了氨基葡萄糖（G-NH2）对酪氨酸酶的抑制作用。在反应液中加入50μL浓度为2.2 mg/mL G-NH2时（体系中G-NH2终浓度为36μg/mL）,酶抑制率为50%。GNH2对酪氨酸酶的抑制作用是个复杂的过程,酶反应呈先促进后抑制。分析酶抑制曲线Lineweaver-Burk双倒数图,得出G-NH2为混合抑制剂,进一步研究发现多巴醌生产量会减少,抑制类型是不可逆抑制。     

银杏外种皮提取物对酪氨酸酶的抑制作用

以银杏外种皮为材料,采用水、乙醇和乙醇-乙醚三种不同的方法分离提取其中的活性物质(分别命名为1#,2#,3#),研究它们对蘑菇酪氨酸酶催化L-多巴(L-DOPA)氧化活力的影响。结果表明,这3种提取物均对蘑菇酪氨酸酶有抑制作用,1#,2#和3#对酶抑制作用的IC50分别为2.25、1.75和0.32mg/mL。抑制作用动力学结果表明:三种提取物对酶的抑制作用均表现为混合型,相应的抑制常数KI依次为2.11、1.62和0.29mg/mL;KIS依次为2.80、2.33和0.45mg/mL。结果显示,采用乙醇-乙醚提取的银杏外种皮提取物对酪氨酸酶抑制作用最强。     

广东蛇葡萄的化学成分研究

从广东蛇葡萄(Ampelopsis cantoniensis)藤茎的乙醇提取物的乙酸乙酯部分离得到13个化合物,经波谱技术鉴定为:白藜芦醇(1)、5,7-二羟基香豆素(2)、山奈酚(3)、二氢木犀草素(4)、槲皮素(5)、二氢槲皮素(6)、没食子酸(7)、杨梅素(8)、二氢杨梅素(9)、槲皮素-3-O-α-L-鼠李糖苷(10)、杨梅素-3-O-α-L-鼠李糖苷(11)、山奈酚-3-O-α-L-鼠李糖苷(12)、表儿茶素-3-O-没食子酸酯(13)。除化合物8和9,其余化合物均为首次从该植物中分离得到。     

八种蜂花粉醇提物对酪氨酸酶的二酚氧化活性的抑制作用

本文研究了杏花花粉、茶花花粉、油菜花粉、向日葵花粉、荷花花粉、荞麦花粉、玫瑰花粉、五味子花粉等八种花粉醇提物对酪氨酸酶的二酚氧化活性的抑制作用.结果表明这八种花粉醇提物对以L-多巴为底物的酪氨酸酶抑制作用,存在显著性差异.其中向日葵花粉醇提物表现出最好的抑制作用,IC50为(0.303±0.003)mg/mL,五味子花粉醇提物的抑制作用相对较弱,IC50为(1.946±0.045)mg/mL.     

十种蜂花粉醇提物对酪氨酸酶的二酚氧化活性抑制作用研究

本实验主要研究了五味子、桃花、蒲公英、山楂、野藿香、山花、黄柏、野玫瑰、黄玫瑰、野菊花十种蜂花粉醇提物对酪氨酸酶二酚氧化活性的抑制作用。结果表明：这十种蜂花粉醇提物对酪氨酸酶均有明显抑制作用,抑制率随着蜂花粉醇提物浓度的提高而提高。其中野玫瑰、黄柏、蒲公英花粉醇提物对两步催化氧化作用都有较好的抑制作用;五味子和野藿香花粉醇提物对酪氨酸酶二酚氧化活性有较好的抑制作用。     

王锦蛇血清对尖吻蝮蛇毒的抑制作用

目的 探讨王锦蛇血清对尖吻蝮蛇毒的抑制作用。方法 王锦蛇血清与不同剂量的尖吻蝮蛇毒分别混合后,注射到小鼠背皮下,测定王锦蛇血清对尖吻蝮蛇毒的抗出血活力;腹腔注射此混合物后,测定王锦蛇血清对尖吻蝮蛇毒的抗毒效价;先后注射尖吻蝮蛇毒和王锦蛇血清,测定王锦蛇血清对尖吻蝮蛇毒引起的死亡、组织损伤和炎症的抑制、保护和治疗作用。结果 1ml王锦蛇血清可完全抑制10mg（干重）的尖吻蝮蛇毒的出血活力;1ml王锦蛇血清可中和11mg（干重）尖吻蝮蛇毒的致死活力;王锦蛇血清对由尖吻蝮蛇毒引起的致死、组织损伤和炎症有显著的抑制、保护和治疗作用。结论 王锦蛇血清是尖吻蝮蛇毒的强抑制剂,可能成为未来新的蛇伤治疗药物的原料。     

显齿蛇葡萄(藤茶)化学成分研究

从显齿蛇葡萄的乙酸乙酯提取物中分离得到9个化合物,经波谱分析、化学分析及与已知化合物对照,分别鉴定为：棕桐酸（1）、β－谷甾醇（2）、大黄素（3）、没食子酸甲酯（4）、槲皮素（5）、槲皮素－3－0－β－D－葡萄糖甙（6）、花旗松素（7）、洋芹素（8）和蛇葡萄素（9）。9个化合物均为首次从该植物中分离得到。     

Effects of 4-Tertiary Butylphenol on the Tyrosinase Activity in Human Melanocytes

Vitiligo is a common dermatological disorder characterized by the development of complete pigment loss from focal lesions that tends to increase in size over time. The etiology of vitiligo, resulting in the disappearance of functional melanocytes from involved skin, is not clearly understood. As a consequence, no satisfactory therapy has been developed. A subtype of vitiligo, termed‘occupational’or‘contact’vitiligo, is increased in individuals who are exposed to materials containing phenolic derivatives, such as 4-tertiary butylphenol (4-TBP). Phenolic derivatives are structurally similar to tyrosine, the initial substrate of tyrosinase in the biochemical synthesis of melanin. Therefore, it has been proposed that phenolic derivatives compete with tyrosine for hydroxyla-tion by tyrosinase and interfere with the completion of melanin synthesis and/or generate cytotoxic intermediates. Our results demonstrated that 4-TBP competitively inhibited both tyrosine hydroxylase and dihydrox-yphenylalanine (DOPA) oxidase activities of tyrosinase, i.e., the first two catalytic steps in the biochemical conversion of tyrosine to melanin in cultured human melanocytes. This inhibition occurred at concentrations that did not influence the viability of melanocytes. The tyrosinase activity inhibited by 4-TBP was recovered after removing the treatment. 4-TBP did not affect the function of other enzymes, such as succinate-tetra-zolium reductase, acid phosphatase and sulfatase. Since depigmentation occurred without a cytotoxic response after exposure of melanocytes to low concentration of 4-TBP, it is unclear whether the interaction between 4-TBP and tyrosinase leads to the destruction of the melanocytes in‘contact/occupational’vitiligo.     

三叶木通(Akebia trifoliata)果实乙醇提取物对酪氨酸酶体外活性的影响

以人工栽培条件下三叶木通(Akebia trifoliata)果实为试材,用80%乙醇分别提取果皮、果肉、种子中的有效成分,经离心过滤后,于旋转蒸发仪上减压蒸馏浓缩,再经真空干燥处理得到三叶木通乙醇提取物。以L-DOPA为底物,熊果苷作阳性对照,分析测定了该提取物对酪氨酸酶活性的抑制百分率。结果表明:不同部位的三叶木通果实乙醇提取物对酪氨酸酶活性均有一定的抑制作用,其中果肉对酪氨酸酶活性的抑制作用最佳,中等浓度的果肉乙醇提取物(200μg/mL)与270μg/mL的熊果苷对酪氨酸酶活性的抑制率相当。     

An Integrated Study of Tyrosinase Inhibition by Rutin: Progress using a Computational Simulation

Abstract

Tyrosinase inhibition studies have recently gained the attention of researchers due to their potential application values. We simulated docking (binding energies for AutoDock Vina: ?9.1 kcal/mol) and performed a molecular dynamics simulation to verify docking results between tyrosinase and rutin. The docking results suggest that rutin mostly interacts with histidine residues located in the active site. A 10 ns molecular dynamics simulation showed that one copper ion at the tyrosinase active site was responsible for the interaction with rutin. Kinetic analyses showed that rutin-mediated inactivation followed a first-order reaction and mono- and biphasic rate constants occurred with rutin. The inhibition was a typical competitive type with K_i = 1.10 ± 0.25 mM. Measurements of intrinsic and ANS-binding fluorescences showed that rutin showed a relatively strong binding affinity for tyrosinase and one possible binding site that could be a copper was detected accompanying with a hydrophobic exposure of tyrosinase. Cell viability testing with rutin in HaCaT keratinocytes showed that no toxic effects were produced. Taken together, rutin has the potential to be a potent antipigment agent. The strategy of predicting tyrosinase inhibition based on hydroxyl group number and computational simulation may prove useful for the screening of potential tyrosinase inhibitors.     

Tyrosinase inhibition by some flavonoids: Inhibitory activity,mechanism by in vitro and in silico studies

Flavonoids are main polyphenolic groups widely distributed to fruits, vegetables and beverages we consumed daily. They exhibit many biological effects. We tested tyrosinase inhibitor potential of structurally related (1–9) flavonoids and found that all the tested materials possessed tyrosinase inhibitory effect compared to the positive control, kojic acid. 2 exhibited the strongest tyrosinase inhibitory effect with an IC₅₀ value of 40.94 ± 0.78 µM in a competitive manner. According to kinetic analysis 1, 4 and 7 were found to be competitive inhibitors, 3, 5, and 6 noncompetitive inhibitors of tyrosinase. According to the docking studies, A and C ring of the flavonoid structure, hydroxyl substituent at the 7th position, and hydroxyl substituents at para or para and meta position of ring B play key role for competitive inhibition of the enzyme.     

Tyrosinase Isoenzymes: Two Melanosomal Tyrosinases With Different Kinetic Properties and Susceptibility to Inhibition by Calcium

Two forms of tyrosinase from B16 mouse melanoma were identified by nonreducing SDS-PAGE after solubilization of crude melanosomal preparations with the nonionic detergent Brij 35. These forms, named LEMT and HEMT (low and high electrophoretic mobility tyrosinase, respectively), were purified by a combination of differential detergent extraction and chromatographic techniques. They displayed tyrosine hydroxylase and dopa oxidase activity and were stereospecific and sensitive to phenylthiourea, proving that they are true tyrosinases. However, based on its kinetic parameters, HEMT is a much more efficient enzyme, Immunoprecipitation and Western blots performed with the specific antibody αPEP1, directed against the b protein carboxyl terminus, suggested that LEMT is identical to the b protein. Both forms of tyrosinase were noncompetitively inhibited by Ca²⁺ at physiologically relevant concentrations. However, the b protein was apparently more susceptible, since maximal inhibition was reached at lower Ca²⁺ concentrations for LEMT. Moreover, binding of Ca²⁺ to the tyrosinases resulted in a noticeable thermal destabilization of the enzymes, which was also more pronounced for LEMT.     

酪氨酸酶的应用研究进展

酪氨酸酶具有重要的生理生化特性,在医药、环境、食品、精细化工等领域具有广泛的用 途。酪氨酸酶可以氧化L-酪氨酸合成L-多巴和黑色素,L-多巴用于帕金森症的治疗,黑色素能够 杀死HIV病毒。酪氨酸酶可用于环境工程领域处理含苯酚及胺类废水,用于精细化工领域催化 有机合成反应。综述了酪氨酸酶在各个领域的应用概况,阐明了其在工业生产领域的应用前景。     

Inhibitory Kinetics of Azachalcones and their Oximes on Mushroom Tyrosinase: A Facile Solid‐state Synthesis

A solid‐state‐based mechanochemical process was used to synthesize novel azachalcones and their oximes as tyrosinase inhibitors. Their inhibitory activities on mushroom tyrosinase using l ‐3,4‐dihydroxyphenylalanine as a substrate were investigated. Two of the novel oxime derivatives synthesized were seen to be more potent than the positive control, kojic acid. Both the compounds 1b and 2b inhibited the diphenolase activity of tyrosinase in a dose‐dependent manner with their IC₅₀ values of 15.3 and 12.7 μm , respectively. The kinetic analysis showed that their inhibition mechanism was reversible. Both the novel oxime compounds displayed competitive inhibition with their K_i values of 5.1 and 2.5 μm , respectively. This method minimizes waste disposal problems and provides a simple, efficient, and benign method for the synthesis of novel tyrosinase inhibitors for use as skin‐whitening agents or as anti‐browning food additives.     

杨梅素对小鼠梗死后心肌重塑和心力衰竭的影响及机制

目的:探讨杨梅素对小鼠梗死后心肌重塑和心力衰竭的影响及调控机制。方法:结扎左冠状动脉前降支建立心肌梗死的模型,将雄性C57/BL6J小鼠随机分为3组(每组20只):假手术组、心肌梗死组、心肌梗死+杨梅素组。心肌梗死+杨梅素组给予杨梅素250 mg/kg/d灌胃,假手术组和心肌梗死组给予同体积5%羧甲基纤维素钠灌胃。药物治疗1月后,小鼠心脏超声检测心功能;Masson染色评估胶原容积分数(collagen volume fraction,CVF);电镜检测心肌线粒体损伤;Western blot检测p-Mst1、LC3和p62的表达。结果:与假手术组相比,心肌梗死组心功能显著降低(P0.05),心肌ANP和BNP mRNA水平显著增高(P0.05),CVF显著增高(P0.05),线粒体明显肿胀,p-Mst1表达和LC3Ⅱ/LC3Ⅰ比率显著增高(P0.05),p62表达显著降低(P0.05);与心肌梗死组相比,心功能显著增加(P0.05),心肌ANP和BNP mRNA水平显著降低(P0.05),CVF显著降低(P0.05),线粒体超微结构有显著改善,p-Mst1、p62表达显著降低(P0.05),LC3Ⅱ/LC3Ⅰ比率显著增高(P0.05)。结论:杨梅素可能通过抑制Mst1减轻小鼠梗死后心肌重塑和心力衰竭。     

Evolution of the Tyrosinase Related Gene (TYRL) in Primates

Tyrosinase is the major enzyme responsible for the formation of melanin pigment and is found throughout the animal kingdom. In humans, the tyrosinase gene (TYR) maps to the long arm of chromosome 11 at band q14→q21, while a tyrosinase related gene (TYRL) maps to the short arm of chromosome 11 at pll.2°Cen. We and others have found that the TYRL locus contains sequences that are similar to exons IV and V of the authentic tyrosinase gene but lacks sequences of exons I, II, and III. In an attempt to understand the evolution of the human tyrosinase gene, we have analyzed TYR and TYRL in primates and have found that exons IV and V of the chimpanzee and gorilla TYR are very similar to the human, with the gorilla sequence being more similar than the chimpanzee. We have also found that the gorilla but not the chimpanzee contains a TYRL locus similar to the human TYRL locus.     

杨梅素对高脂喂养小鼠代谢及自发活动节律的影响研究

摘要 目的：探讨杨梅素对高脂喂养小鼠代谢情况及自发活动节律的影响。方法：6周龄清洁级C57BL/6雄性小鼠15只,随机分为普通饲料组（CON）、高脂饲料组（HFD）、高脂饲料+杨梅素组100 mg /（kg?d）组（HFD+MYR）。从干预第10周开始使用Clocklab生物节律采集分析系统记录三组小鼠自发活动数据。干预第13周结束,检测三组小鼠体重、血脂数据。结果：与CON组相比,HFD组体重、甘油三酯、总胆固醇、低密度脂蛋白均显著升高（P<0.001）,高密度脂蛋白显著降低（P<0.001）,活动峰值时相（Activity phase）显著后移（P<0.001）,自发活动量中值（Activity mesor）和总自发活动量（Total counts）明显增加（P<0.05）,HFD+MYR组体重和低密度脂蛋白无明显变化（P>0.05）,甘油三酯、总胆固醇均显著升高（P< 0.01）,高密度脂蛋白显著降低（P<0.01）,活动峰值时相显著后移（P<0.001）,自发活动量中值和总自发活动量无明显变化（P>0.05）。与HFD组相比,HFD+MYR组体重、甘油三酯、总胆固醇、低密度脂蛋白明显降低（P<0.05）,高密度脂蛋白明显升高（P<0.05）,活动峰值时相明显前移（P<0.05）,自发活动量中值和总自发活动量明显减少（P<0.05）。结论：杨梅素可改善高脂喂养小鼠的代谢状态及减轻小鼠自发活动节律紊乱。